Swine flu has infected more than a million Americans, federal health officials said Friday, and is infecting thousands more every week even though the annual flu season is well over.

That total of those who have already been infected is “just a ballpark figure,” said Dr. Anne Schuchat, director of respiratory diseases at the Centers for Disease Control and Prevention, adding, “We know we’re not tracking every single one of them.”

Only a tiny fraction of those million cases have been tested, Dr. Schuchat said. The estimate is based on testing plus telephone surveys in New York City and several other locales where the new flu has hit hard.

A survey in New York City, she said, showed that almost 7 percent of those called had had flu symptoms during just three weeks in May when the flu was spreading rapidly through schools. If that percentage of the city has had it, then there have been more than 500,000 cases in the city alone, though most have been mild enough that doctors recommended nothing more than rest and fluids.

The flu has now spread to many areas of the country, Dr. Schuchat noted, and the C.D.C. has heard of outbreaks in 34 summer camps in 16 states.

About 3,000 Americans have been hospitalized, she said, and their median age is quite young, just 19. Of those, 127 have died.

The median age for deaths is somewhat higher, at 37, but that number is pushed up because while only a few elderly people catch the new flu, about 2 percent of them die as a result.

Of those who die, Dr. Schuchat said, about three-quarters have some underlying condition like morbid obesity, pregnancy, asthma, diabetes or immune system problems. Even those victims, she said, “tend to be relatively young, and I don’t think that they were thinking of themselves as ready to die.”

The new flu has now reached more than 100 countries, according to the World Health Organization. The world’s eyes are on the Southern Hemisphere, which is at the beginning of its winter, when flu spreads more rapidly. Australia, Chile and Argentina are seeing a fast spread of the virus, mostly among young people, while one of the usual seasonal flus, an H3N2, is also active.

Five American vaccine companies are working on a swine flu vaccine, Dr. Schuchat said. The C.D.C. has estimated that once the new vaccine is tested for both safety and effectiveness, no more than 60 million doses will be available by September. That means difficult decisions will have to be made about whom to give it to first.

(Source: NY Times)